PRECISE AIRBORNE LIDAR SURVEYING FOR COASTAL RESEARCH AND GEOHAZARDS APPLICATIONS

Abstract

The monitoring and analysis of many natural hazards requires repeated measurements of a topographic surface whose change reflects some geologic or hydrologic process. The development of airborne laser surface mapping (ALSM) allows the study of natural hazards over areas tens to hundreds of kilometers in extent with a horizontal resolution of 1 meter or less and a vertical accuracy of 0.10-to-0.15m. Change detection requires that repeated ALSM surveys be precise and accurate. Repeatability is a function of the stability and calibration of the instrument, the accuracy of GPS aircraft trajectories, the density and completeness of ALSM data coverage, the availability of “ground truth” information, and the accuracy and flexibility of ALSM data classification. Since 1997 The University of Texas at Austin (UT) has mapped various portions of the Texas Gulf coast using several small-footprint, scanning ALSM systems developed by Optech, Inc. During summer 2000, UT comprehensively mapped the Texas coast from Sabine Pass on the Texas-Louisiana border to the mouth of the Rio Grande River. These data provide a series of Gulf shorelines for estimating beach erosion rates and computing volumetric sand loss. The high-resolution beach and dune topography derived from ALSM will help characterize the susceptibility of the coast to hurricane overwash and storm-related flooding. In another project UT collaborated with Optech and the U.S. Geological Survey in March 2000 to survey fifteen municipalities in Honduras with ALSM as part of the USAID Hurricane Mitch Recovery program. Digital elevation models produced from these data are being used for flood and landslide hazard analysis. During these and other projects, UT began implementing procedures for instrument